EOSC 112 THE FLUID EARTHS ENERGY BUDGET AND

EOSC 112: THE FLUID EARTH’S ENERGY BUDGET AND CLIMATE FEEDBACKS E 3 Read: Kump et al. Chap. 3, p. 44 (Atm. Comp. ), p. 46 -53. Check: Key Terms, Review Questions 5, 6, 8 -12, Problems 4, 5, 6. Objectives: 1. To describe the physical causes of the greenhouse effect 2. To describe the global energy budget and the role of clouds 3. To model radiative climate feedbacks

1. Greenhouse Effect (Atm. Comp. ) • Major constituents: (concentration by volume) – N 2 78%, O 2 21%, Ar 0. 9 % – H 2 O up to 4% (tropics), CO 2 0. 037% A gas is called a “greenhouse gas” if it is able to absorb and emit infrared radiation. • Greenhouse gases: – H 2 O, CO 2 – Minor or “trace” constituents: Methane CH 4, Nitrous oxide N 2 O, Ozone O 3, Freon-11 CCl 3 F, Freon-12 CCl 2 F 2

Physical causes of the greenhouse effect Molecules can only rotate at certain discrete frequencies. Only a photon of the right frequency (wavelength) can be absorbed to increase a molecule’s rotational frequency.

2. Mechanisms of Heat Transfer Radiation: can transfer heat over vacuum. Conduction: … via neighboring molecules. Convection: … by fluid movement, especially overturning. It is much stronger than conduction in atmosphere

Earth’s Energy Budget

Cumulus Cumulonimbus Stratus Cirrus

Role of Clouds Low, thick clouds (stratus-type) cool the surface; High, thin clouds (cirrus-type) warm the surface.

3. Radiative Climate Feedbacks Water vapor feedback: It is observed that for most regions of the planet, water vapor is close to its point of condensation. Small changes in surface T will cause similar changes in atmospheric vapor H 2 O concentrations and vice versa. Result: 2 positive couplings positive feedback loop!

Unclear figure representing water vapor feedback

Snow/Ice Albedo Feedback: Small changes in surface T will cause opposite changes in the extent of polar ice cover and vice versa. Result: 2 negative couplings positive feedback loop!

Infrared Flux-Ts Feedback: This feedback mechanism is responsible for the shortterm stability of our climate. Compare this feedback loop to that of our “Soot Planet”!